In recent years, in mobile wireless communication terminals such as mobile phones or PDA's (personal digital assistants), lower power consumption, smaller size, and lighter weight have been realized. Realization of multi-band and multi-mode functions is inevitable. Along with this, such multi-band compatible mobile wireless communication terminals are being provided with wireless signal switching circuits for switching a plurality of wireless transmitter signals or a plurality of wireless receiver signals. In such wireless signal switching circuits, reduction of loss at the time of switching among a plurality of routes and in routes has been strongly demanded.
Referring to the document “Chip Multilayer Antenna Switch Module for Triple Band Phone (EGSM/DCS/PCS)”, see HITACHI METALS, URL: http://www.hitachi-metals.co.jp/product/isc2001/asm/shs1090t.pdf, an example of signal switching in a wireless signal switching circuit used in a mobile phone (cellular phone) or other mobile wireless communication terminal will be explained. For example, a case of using three frequencies F1, F2 and F3 as the multi-bands will be explained. However, assume that the frequencies have a relationship of F1<<F2<F3. For example, F1=900 MHz, F2=1800 MHz, and F3=1900 MHz.
In the wireless signal switching circuit illustrated in FIG. 1, a diplexer 102 directly connected to an antenna terminal 101 of a wireless transmitter and receiver antenna ANT roughly divides a frequency domain of the transmitter and receiver signal into two. Namely, the diplexer 102 divides the frequency domain into a frequency F1 having a low frequency and frequencies F2 and F3 having a high frequency.
A switch element 103 separates a transmitter signal F1TX and a receiver signal F1RX of the frequency F1. The transmitter signal F1TX of the frequency F1 is applied to the switch element 103 through a low pass filter 106 and transmitted from the wireless transmitter and receiver antenna ANT through the diplexer 102. The receiver signal F1RX of the frequency F1 received at the wireless transmitter and receiver antenna ANT is divided in frequency at the diplexer 102 and output from the switch element 103.
The switch element 104 separates the transmitter signal F2 or F3TX of the frequency F2 or F3 (F2/F3), and the receiver signal F2RX of the frequency F2 and the receiver signal F3RX of the frequency F3. The transmitter signal F2 or F3TX of the frequency F2 or F3 is applied to the switch element 104 through the low pass filter 107 and transmitted from the wireless transmitter and receiver antenna ANT through the diplexer 102. The receiver signal F2 or F3RX of the frequency F2 or F3 received at the wireless transmitter and receiver antenna ANT is separated at the diplexer 102 and output from the switch element 104. Further, the switch element 105 separates the receiver signal F2RX of the frequency F2 and the receiver signal F3RX of the frequency F3.
The wireless signal switching circuit explained above employs a configuration roughly dividing the frequency domain into two at first by using the diplexer 102, then switching routes of frequencies by using switch elements 103 to 105, therefore requires many switch elements. For example, at the reception side of the frequency F2 or F3, signals pass through the diplexer 102, the switch element 104 and the switch element 105, so the losses at the switch elements accumulate resulting in a larger attenuation of the receiver signal. The attenuation of the receiver signal causes the disadvantages of the necessity of adding a signal amplifier circuit and susceptibility to noise.
In the example explained above, there were three types of frequency, but the larger the type of the frequency to be used, the larger the number of switches for switching the routes accompanied with that. When a PIN (positive intrinsic negative) diode, for example, as such a switch element is used, the power consumption becomes large.
When using such a wireless signal switching circuit in a mobile phone or other wireless communication apparatus, the power consumption of the wireless communication apparatus becomes large. For example, a mobile phone is driven by a battery, therefore the increase of the power consumption causes the disadvantage such as shortening of the service life of the battery.